Recurrent corneal erosion typically occurs in eyes that have suffered a sudden sharp, abrading injury (e.g., fingernail, edge of paper, etc.). The superficial injury produces an epithelial abrasion which heals rapidly, leaving no clinical evidence of damage. After an interval varying from days to years, symptoms suddenly recur in the absence of any obvious cause. In most instances they again subside promptly, only to recur periodically. In contrast to shearing injuries, small and partially penetrating foreign bodies which strike the cornea directly and become embedded in the epithelium or superficial stroma rarely produce recurrent erosions. Some patients recall no injury and have an inherited potential for superficial degeneration of the cornea (i.e., basement membrane disease).
Repeated episodes of foreign body sensation, tearing, photophobia, and pain describe recurrent corneal erosion which has been a most frustrating condition to treat. These episodes mainly occur in the early morning hours upon awakening. However, these episodes can occur at any other time of day as well. A classic example would be trauma to the cornea by a tree branch or fingernail. When the epithelium attempts to heal over, the epithelium does not heal well and the cells slough off. However, this can occur in a non traumatic eye as well. The poor adhesions on the epithelium are caused by deeper adhesions in the cornea.
Objective signs of recurrent corneal erosion vary from a localized roughening of the epithelium to a true abrasion. The less severe corneal signs resolve rapidly; and often, when the patient is examined within hours of an acute recurrence, no abnormality is discernible. It is recognized that the corneal epithelium is loosely attached to its basement membrane and to Bowman's layer, both at the time of a recurrent attack and between attacks when the cornea appears to be entirely healed.
The first and most common treatment for recurrent corneal erosion is the consistent use of lubricating ointment and frequent instillation of artificial tear drops. Patching is also useful. Also, because of the frequent occurrence of these episodes further methods of treatment are used. Bandage contact lenses have been used with some success as well, but they have been associated with infectious keratitis. Superficial epithelial keratectomy or scraping of Bowman's layer has been somewhat effective, but these treatments have also resulted in multiple spontaneous corneal erosions. As with anterior stromal puncture, such treatment involves making multiple penetrations into the anterior corneal stroma in order to generate secure adhesions between the epithelium and the deeper corneal structures. Drawbacks of this procedure include the risk of perforation, and patient apprehension that results when the patient is approached with a needle while sitting at the slit lamp.
Yag lasers are also used as a form of treatment for recurrent corneal erosion. With each laser application, a small bubble is formed beneath the epithelium. However, if the application is placed too posteriorly, a small stromal lesion occurs. Conversely, if the application is placed too anteriorly, a spark will be seen in front of the cornea.
The Excimer laser has also been shown to be effective in treating corneal erosions. With this procedure the entire corneal surface is lasered leaving the nerves exposed which is extremely painful for the patient. This technique is also much more expensive for the physician to perform as well as for the patient to recompense.
It is an object of the present invention to provide an improved procedure for treating recurrent corneal erosion that does not suffer from the drawbacks of prior treatment methods.
In particular, it is object of the present invention to provide an effective treatment for corneal erosion that is relatively painless for the patient, causes minimal patient apprehension, and minimizes the risk of collateral injury to the eye as a result of the treatment.
It is a still further object of the present invention to provide an effective treatment for recurrent corneal erosion that can be performed relatively quickly and at a reasonable cost to the patient.
It is a still further object of the present invention to provide an effective treatment for eye abnormalities other than those relating to recurrent corneal erosion. For example, it is an object of the present invention to provide alternative treatments for patients suffering from swelling of the cornea or from bullous keratopathy.
It is a still further object of the present invention to provide a general method for illuminating an epithelium layer with laser light without damaging the underlying tissue layers beneath the epithelium. The epithelium layer treated may be on the cornea, or alternatively at some other site on the body.
These and other objects and advantages of the invention will become more fully apparent from the description and claims which follow or may be learned by the practice of the invention.